Metformin for Asthma in Overweight and Obese Adults

Inclusion Criteria: * Physician-diagnosed asthma on maintenance therapy * Not well-controlled asthma (ACT score \<20, or at least one asthma exacerbation requiring corticosteroids in the prior 12 months) * Overweight or obesity: Body mass index ≥25kg/m2 * Adult: Age ≥18 Exclusion Criteria: * Currently pregnant, expect to become pregnant in the next 6 months or are currently breastfeeding * Major cardiovascular disease: heart failure, heart attack or stroke within the last 6 months * Other chronic lung disease, inclusive of chronic obstructive pulmonary disease, bronchiectasis, interstitial lung disease, pulmonary fibrosis * Active smoking or former smoker with ≥20 pack-year smoking history * Chronic kidney disease: estimated glomerular filtration rate ≤60 mL/min/1.73 m2 * Heavy alcohol use: in a typical week, 8 or more drinks for a woman or 15 or more drinks for a man * Liver disease: elevation in aspartate aminotransferase (AST) or alanine aminotransferase (ALT) \> 2x the upper limit of normal or prior diagnosis of liver disease * Anemia: hemoglobin \< 13 g/dl in males and hemoglobin \< 11 g/dl in females * Taking Glucagon Like Peptide 1(GLP-1) medications for weight loss * Diabetes (Hemoglobin A1C ≥ 6.5% or taking metformin or other medications used to treat diabetes) * Participation in any other clinical trial (observational studies are permitted)